In recent years, the market for electronic devices, such as mobile communication terminals, PDAs (Personal Digital Assistants), and auto navigation systems has expanded through the development of various electronic devices having various functions. In order obtain a thin structure with a large display area, most recent electronic devices employ a touch panel display, enabling an increase in display area and providing a user friendly input means. In particular, with rapid expansion of the smartphone market, demand for touch panel type display devices has increased.
Specifically, a touch panel is a device that functions as a data input unit used in a variety of office devices such as computers, word processors or personal digital assistants, and is now considered an essential feature in a variety of electronic devices in consideration of modern emphasis on usability. In particular, the touch panel is incorporated into a display device for displaying data so as to allow intuitive manipulation thereof.
Touch panels include a resistive layer type, an optical type, electrostatic capacitive type, ultrasound wave type, and the like. Among these, the resistive layer type touch panel and the electrostatic capacitive type touch panel are generally used.
Such a touch panel is secured to a display device module via a pressure-sensitive adhesive layer formed in a lattice shape along an edge of the display device module. FIG. 1 is a schematic sectional view of a conventional touch panel type display device. Referring to FIG. 1, a touch panel 11 is coupled to a display device module 13 via a pressure sensitive adhesive layer 12 to constitute a touch panel type display device 10. In this structure, however, an air gap 14 is present between the touch panel 11 and the display device module 13, causing deterioration in visibility through increase in reflectivity.
In order to solve such a problem in the art, the touch panel can be directly bonded to a liquid crystal display module using a double-sided adhesive sheet. However, when a conventional pressure-sensitive double-sided adhesive sheet is used in the air gap 14, the display device module 13 and the touch panel 11 cannot be separated from each other in the event that repairs need to be made, causing the expensive display device module to be discarded.
Therefore, there is a need for a double-sided adhesive sheet, which can improve visibility of a display device by eliminating an air gap between a touch panel and a display device module, and can ensure that the touch panel and the display device can be properly reattached therethrough after separation from one another.